A fixed focus lens

Abstract

The application discloses a fixed-focus lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence along an optical axis from an object plane to an image plane; the object side surface of the first lens is a convex surface, and the image side surface is a concave surface; the object side surface of the second lens is a convex surface, and the image side surface is a concave surface; the object side surface of the third lens is a concave surface, and the image side surface is a convex surface; and the object side surface of the eighth lens is a convex surface, and the image side surface is a convex surface. By arranging the fixed-focus lens to comprise eight lenses and by reasonably arranging the surface shapes of the first lens, the second lens, the third lens and the eighth lens, the machining difficulty of the lens is reduced, the illumination of the lens and the sensitivity of the lens are improved, the aberration of the lens is balanced, the imaging effect of the fixed-focus lens is improved, and the characteristics of being capable of matching a 1'' target surface sensor chip and being capable of giving consideration to wide angle and low distortion and the maximum image surface being up to 16.1 mm are achieved.

Description

Technical Field

[0001] The present invention relates to the field of optical device technology, and in particular to a fixed-focus lens. Background Technology

[0002] As the market becomes increasingly demanding in terms of lens parameters and performance, wide-angle lenses are widely used in industries such as surveillance, photography, and automotive, due to their ability to provide a wider field of view and a significantly greater depth of field than standard lenses.

[0003] However, as the field of view increases, lens distortion also increases, resulting in severe image distortion. Therefore, reducing lens distortion while maintaining a large field of view becomes a challenge that needs to be overcome. Summary of the Invention

[0004] This invention provides a fixed-focus lens design that achieves a wide angle of view and low distortion.

[0005] This invention provides a fixed-focus lens, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis from the object plane to the image plane;

[0006] The first lens includes a first object-side surface near the object plane and a first image-side surface near the image plane. The first object-side surface is convex, and the first image-side surface is concave.

[0007] The second lens includes a second object-side surface near the object plane and a second image-side surface near the image plane, wherein the second object-side surface is convex and the second image-side surface is concave.

[0008] The third lens includes a third object-side surface near the object plane and a third image-side surface near the image plane, wherein the third object-side surface is concave and the third image-side surface is convex.

[0009] The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane. The eighth object-side surface is convex, and the eighth image-side surface is convex.

[0010] Optionally, the fourth lens includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane; the fourth object-side surface is concave and the fourth image-side surface is convex.

[0011] The fifth lens includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane; the fifth object-side surface is convex, and the fifth image-side surface is convex.

[0012] The sixth lens includes a sixth object-side surface near the object plane and a sixth image-side surface near the image plane; the sixth object-side surface is concave and the sixth image-side surface is concave.

[0013] The seventh lens includes a seventh object-side surface near the object plane and a seventh image-side surface near the image plane; the seventh object-side surface is convex and the seventh image-side surface is convex.

[0014] Optionally, the first lens, the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all glass spherical lenses, and the third lens and the eighth lens are both plastic aspherical lenses.

[0015] Optionally, the sixth lens and the seventh lens are cemented together to form a cemented lens.

[0016] Optionally, the first lens has negative optical power; the second lens has negative optical power; the third lens has negative optical power; the fourth lens has positive optical power; the fifth lens has positive optical power; the sixth lens and the seventh lens are cemented together to form a cemented lens, the cemented lens having negative optical power; and the eighth lens has positive optical power.

[0017] Optionally, the optical power of the fixed-focus lens is... The first lens has an optical power of The second lens has an optical power of The optical power of the third lens is The optical power of the fourth lens is The optical power of the fifth lens is The optical power of the cemented lens is: The optical power of the eighth lens is:

[0018] in:

[0019] Optionally, the refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n2, the refractive index of the fourth lens is n4, the refractive index of the fifth lens is n5, the refractive index of the sixth lens is n6, the refractive index of the seventh lens is n7, and the refractive index of the eighth lens is n8.

[0020] Among them, 1.72≤n1≤1.87; 1.57≤n2≤1.80; 1.49≤n3≤1.74; 1.54≤n4≤1.80; 1.49≤n5≤1.67; 1.70≤n6≤1.84; 1.56≤n7≤1.86; 1.48≤n8≤1.69.

[0021] Optionally, the image plane diameter of the fixed-focus lens is IC, and the total length of the fixed-focus lens is TTL;

[0022] Among them, IC / TTL≥0.24.

[0023] Optionally, the field of view (FOV) of the fixed-focus lens satisfies FOV > 140°.

[0024] Optionally, the fixed-focus lens may also include an aperture stop and a filter;

[0025] The aperture stop is disposed in the optical path between the fifth lens and the sixth lens;

[0026] The filter is disposed in the optical path between the eighth lens and the image plane.

[0027] The fixed-focus lens provided in this embodiment of the invention includes eight lenses. By reasonably setting the surface shapes of the first, second, third, and eighth lenses, it is beneficial to reduce the lens manufacturing difficulty, while improving lens illumination and lens sensitivity, balancing lens aberrations, and improving the imaging effect of the fixed-focus lens. It achieves the characteristics of wide-angle low distortion, a maximum image plane greater than 16.1mm, and compatibility with 1″ target surface sensor chips.

[0028] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0031] Figure 2 This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0032] Figure 3 This is a schematic diagram of distortion in a fixed-focus lens provided in Embodiment 1 of the present invention;

[0033] Figure 4 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0034] Figure 5 This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0035] Figure 6 This is a schematic diagram of distortion of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0036] Figure 7 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0037] Figure 8 This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0038] Figure 9 This is a distortion diagram of a fixed-focus lens provided in Embodiment 3 of the present invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] Example 1

[0041] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of the present invention, as shown below. Figure 1 As shown, the fixed-focus lens provided in Embodiment 1 of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180 arranged sequentially along the optical axis from the object plane to the image plane. The first lens 110 includes a first object-side surface near the object plane and a first image-side surface near the image plane, the first object-side surface being convex and the first image-side surface being concave. The second lens 120 includes a second object-side surface near the object plane and a second image-side surface near the image plane, the second object-side surface being convex and the second image-side surface being concave. The third lens 130 includes a third object-side surface near the object plane and a third image-side surface near the image plane, the third object-side surface being concave and the third image-side surface being convex. The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane, the eighth object-side surface being convex and the eighth image-side surface being convex.

[0042] Specifically, the first object-side surface of the first lens 110 is convex, and the first image-side surface is concave; that is, the object-side surface of the first lens 110 convexes towards the object plane, and the image-side surface is concave towards the image plane, making the first lens 110 a convex-concave lens. The second object-side surface of the second lens 120 is convex, and the second image-side surface is concave; that is, the object-side surface of the second lens 120 convexes towards the object plane, and the image-side surface is concave towards the image plane, making the second lens 120 a convex-concave lens. The third object-side surface of the third lens 130 is concave, and the third image-side surface is convex; that is, the object-side surface of the third lens 130 is concave towards the object plane, and the image-side surface is convex towards the image plane, making the third lens 130 a concave-convex lens. The eighth object-side surface of the eighth lens 180 is convex, and the eighth image-side surface is convex; that is, the object-side surface of the eighth lens 180 convexes towards the object plane, and the image-side surface is convex towards the image plane, making the eighth lens 180 a biconvex lens.

[0043] Furthermore, the first lens 110 can be a meniscus lens. This structure is beneficial for light collection, ensuring a large field of view for the fixed-focus lens and achieving its wide-angle characteristic. The second lens 120 can also be a meniscus lens, similar in shape to the first lens 110, also beneficial for light collection, ensuring a large field of view for the fixed-focus lens and achieving its wide-angle characteristic. The second lens 120 also ensures a small angle of incidence, which helps provide illumination to the fixed-focus lens, further reducing light beam height and lens sensitivity. The third lens 130 can be a meniscus lens, with its crescent shape opposite to that of the first lens 110 and the second lens 120. The third lens 130 can reduce the focal length of the rear lens, balancing aberrations. The biconvex eighth lens 180 can converge the light beam, reducing the angle at which light enters the sensor, increasing the light throughput received by the sensor, and improving sensing performance.

[0044] In summary, the fixed-focus lens provided in this embodiment of the invention, by setting the fixed-focus lens to include eight lenses and by reasonably setting the surface shapes of the first lens, the second lens, the third lens and the eighth lens, helps to reduce the lens manufacturing difficulty, while improving the lens illumination and lens sensitivity, balancing lens aberrations, and improving the imaging effect of the fixed-focus lens. It achieves the characteristics of wide-angle low distortion, a maximum image plane of up to 16.1mm, and compatibility with 1″ target surface sensor chips.

[0045] Based on the above embodiments, continue to refer to Figure 1As shown, the fourth lens 140 includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane, the fourth object-side surface being concave and the fourth image-side surface being convex; the fifth lens 150 includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane, the fifth object-side surface being convex and the fifth image-side surface being convex; the sixth lens 160 includes a sixth object-side surface near the object plane and a sixth image-side surface near the image plane, the sixth object-side surface being concave and the sixth image-side surface being concave; the seventh lens 170 includes a seventh object-side surface near the object plane and a seventh image-side surface near the image plane, the seventh object-side surface being convex and the seventh image-side surface being convex.

[0046] Specifically, the fourth object-side surface of the fourth lens 140 is concave, and the fourth image-side surface is convex. That is, the object-side surface of the fourth lens 140 is concave towards the object plane, and the image-side surface is convex towards the image plane; therefore, the fourth lens 140 is a lens with a concave-convex structure. The fifth object-side surface of the fifth lens 150 is convex, and the fifth image-side surface is convex. That is, the object-side surface of the fifth lens 150 is convex towards the object plane, and the image-side surface is convex towards the image plane; therefore, the fifth lens 120 is a biconvex lens. The sixth object-side surface of the sixth lens 160 is concave, and the sixth image-side surface is concave. That is, the object-side surface of the sixth lens 160 is concave towards the object plane, and the image-side surface is concave towards the image plane; therefore, the sixth lens 160 is a biconcave lens. The seventh object-side surface of the seventh lens 170 is convex, and the seventh image-side surface is convex. That is, the object-side surface of the seventh lens 170 is convex towards the object plane, and the image-side surface is convex towards the image plane; therefore, the seventh lens 170 is a biconvex lens. The shapes of the lenses from the fourth lens 140 to the seventh lens 170 are matched in the manner described above, which is beneficial for the correction of monochromatic aberration, while also ensuring that the entire fixed-focus lens structure is compact and has a high degree of integration.

[0047] Based on the above embodiments, the first lens 110, the second lens 120, the fourth lens 140, the fifth lens 150, the sixth lens 160 and the seventh lens 170 are all glass spherical lenses, and the third lens 130 and the eighth lens 180 are both plastic aspherical lenses.

[0048] Specifically, a spherical lens is characterized by a constant curvature from its center to its periphery, ensuring a simple lens configuration. Furthermore, the spherical lens can be a glass spherical lens; therefore, by using glass spherical lenses for the first lens 110, second lens 120, fourth lens 140, fifth lens 150, sixth lens 160, and seventh lens 170, it is possible to balance high and low temperatures. When the ambient temperature of the fixed-focus lens varies significantly, this helps maintain the stability of the fixed-focus lens's focal length, for example, ensuring stable optical performance between -40℃ and 85℃. Moreover, due to the relatively large thickness of the first lens 110, using a glass spherical lens for the first lens 110 ensures a simple manufacturing process for it.

[0049] Aspherical lenses are characterized by a continuous change in curvature from the center to the periphery, unlike spherical lenses which have a constant curvature. Aspherical lenses offer superior radius of curvature characteristics, improving distortion and astigmatism. Using aspherical lenses can minimize aberrations that occur during image formation, thus enhancing image quality. For example, the third lens 130 and the eighth lens 180 are both aspherical lenses, used to correct off-axis point aberrations, optimize distortion, CRA, and other optical properties, and improve image quality. Furthermore, aspherical lenses can be made of plastic, which simplifies manufacturing processes and reduces costs. Furthermore, since the cost of plastic aspherical lenses is much lower than that of glass spherical lenses, the fixed-focus lens provided in this embodiment of the invention adopts a combination of glass spherical lenses and plastic aspherical lenses, which can effectively control the cost of fixed-focus lenses while ensuring their optical performance; at the same time, the lens materials have a mutual compensating effect, which can ensure normal use in high and low temperature environments.

[0050] Based on the above embodiments, the sixth lens 160 and the seventh lens 170 are cemented together to form a cemented lens.

[0051] Specifically, the sixth lens 160 and the seventh lens 170 are cemented together to form a cemented lens, which can be understood as the image-side surface of the sixth lens 160 being cemented to the object-side surface of the seventh lens 170. Cemented lenses can be used to minimize or eliminate chromatic aberration. Using cemented lenses in fixed-focus lenses can improve image quality and reduce light energy reflection loss, thereby enhancing the sharpness of the lens image. Furthermore, the use of cemented lenses can simplify the assembly process in lens manufacturing, improving equipment efficiency. For example, by introducing a cemented lens composed of the sixth lens 160 and the seventh lens 170, it is possible to help eliminate the effects of chromatic aberration and reduce tolerance sensitivity; at the same time, the cemented lens can also balance the overall chromatic aberration of the optical system. The cementation of the lenses eliminates the air gap between the two lenses, making the overall optical system compact and meeting the requirements of system miniaturization. Moreover, the cementation of the lenses reduces tolerance sensitivity issues such as tilting / eccentricity that occur during the assembly of lens units. Furthermore, the sixth lens 160 and the seventh lens 170 can be supported by a gasket or glued together. The present invention does not limit the specific arrangement of the glued lenses.

[0052] Based on the above embodiments, the first lens 110 has negative optical power; the second lens 120 has negative optical power; the third lens 130 has negative optical power; the fourth lens 140 has positive optical power; the fifth lens 150 has positive optical power; the sixth lens 160 and the seventh lens 170 are cemented together to form a cemented lens, which has negative optical power; and the eighth lens 180 has positive optical power.

[0053] Specifically, optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam, characterizing the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. When the optical power is positive, the refraction of light is converging; when the optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., a surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group). In the fixed-focus lens provided in this embodiment, the first lens 110, the second lens 120, and the third lens 130 are set as negative optical power lenses. This ensures that the first lens 110, the second lens 120, and the third lens 130 can effectively deflect light rays incident at large angles, thereby effectively increasing the field of view of the fixed-focus lens and ensuring that the optical system has wide-angle or even ultra-wide-angle characteristics. Furthermore, the first lens 110 is configured as a negative power lens to control the entrance pupil position to a reasonable level, thereby reducing the lens front aperture. The fourth lens 140 is configured as a positive power lens, enabling it to promptly correct larger aberrations produced by the first lens 110, second lens 120, and third lens 130, particularly effectively correcting edge aberrations in the optical system, thus improving the imaging resolution. The fifth lens 150 is further configured as a positive power lens, and the cemented lens formed by the sixth lens 160 and the seventh lens 170 is negative power, which also helps eliminate aberrations, including field curvature, coma, and astigmatism, further improving the imaging resolution of the optical system. Finally, the eighth lens 180 is configured as a positive power lens, which can promptly correct the image finally projected onto the image plane, particularly effectively correcting edge aberrations in the optical system, thereby improving the imaging effect.

[0054] Based on the above embodiments, the lens optical power is The optical power of the first lens is: The optical power of the second lens is The optical power of the third lens is The optical power of the fourth lens is The optical power of the fifth lens is The optical power of the cemented lens is The optical power of the eighth lens is in:

[0055] By limiting the ratio of the optical power of each lens to that of a fixed-focus lens within a certain range, system aberrations can be corrected and imaging performance improved.

[0056] Based on the above embodiments, the refractive index of the first lens 110 is n1, the refractive index of the second lens 120 is n2, the refractive index of the third lens 130 is n2, the refractive index of the fourth lens 140 is n4, the refractive index of the fifth lens 150 is n5, the refractive index of the sixth lens 160 is n6, the refractive index of the seventh lens 170 is n7, and the refractive index of the eighth lens 180 is n8; wherein, 1.72≤n1≤1.87; 1.57≤n2≤1.80; 1.49≤n3≤1.74; 1.54≤n4≤1.80; 1.49≤n5≤1.67; 1.70≤n6≤1.84; 1.56≤n7≤1.86; and 1.48≤n8≤1.69.

[0057] Specifically, the refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium. It is mainly used to describe a material's ability to refract light, and different materials have different refractive indices. By setting the refractive indices of the first lens 110 to the eighth lens 180 within the aforementioned range, system aberrations can be further corrected, and imaging effects can be improved.

[0058] Based on the above embodiments, the image plane diameter of the fixed-focus lens is IC, and the total length of the fixed-focus lens is TTL; wherein, IC / TTL ≥ 0.24. This allows for an increase in the target area of ​​the optical system while ensuring its performance.

[0059] Based on the above embodiments, the field of view (FOV) of the fixed-focus lens satisfies FOV > 140°, that is, the fixed-focus lens is a wide-angle lens.

[0060] Based on the above embodiments, the fixed-focus lens also includes an aperture stop 190 and a filter 200; the aperture stop 190 is disposed in the optical path between the fifth lens 150 and the sixth lens 160; the filter 200 is disposed in the optical path between the eighth lens 180 and the image plane.

[0061] Specifically, by setting the aperture stop 190, the propagation direction of the light beam can be adjusted, which helps to improve image quality. Furthermore, in this fixed-focus lens, the aperture stop 190 can be located in the optical path between the fifth lens 150 and the sixth lens 160. Positioning the aperture stop 190 in the middle of the fixed-focus lens ensures that the front and rear apertures of the lens are minimized. Further, the filter 200 is positioned in the optical path between the eighth lens 180 and the image plane. The filter 200 can filter out stray spectra, ensuring image quality. Additionally, the fixed-focus lens may also include a flat glass plate, which serves to protect the lens and the image sensor.

[0062] As a feasible implementation method, the parameters of each lens in the fixed-focus lens will be explained next.

[0063] Table 1. Optical design values ​​for a fixed-focus lens in Example 1.

[0064]

[0065] Table 2. Design values ​​for the surface type, radius of curvature, thickness, refractive index, Abbe number, and semi-diameter of each lens in a fixed-focus lens.

[0066] Face number Surface type radius of curvature thickness Materials (nd) Materials (vd) Half diameter S1 spherical 51.070 2.321 24.811 S2 spherical 21.650 1.334 1.768 80.001 15.960 S3 spherical 9.484 8.641 9.482 S4 spherical 60.613 0.700 1.617 80.000 9.418 S5 spherical 11.719 7.403 8.029 S6 aspherical -21.771 4.833 1.684 19.000 7.481 S7 aspherical -24.746 0.208 7.350 S8 spherical -83.508 7.997 1.595 22.148 7.131 S9 spherical -32.402 2.521 6.800 S10 spherical 8.317 7.115 1.536 94.500 5.000 S11 spherical -101.216 3.658 3.619 STO spherical PL 0.825 2.021 S13 spherical -4.869 0.687 1.786 27.999 2.600 S14 spherical 10.256 1.673 1.813 94.501 3.095 S15 spherical -12.064 0.097 3.463 S16 aspherical 13.857 7.256 1.641 23.001 6.000 S17 aspherical -12.091 0.100 5.362 S18 spherical PL 1.650 1.517 64.212 5.604 S19 spherical PL 6.792±0.5 5.945

[0067] In Table 2 above, the surface numbers are assigned according to the surface order of each lens. "S1" represents the object-side surface of the first lens, "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture stop of the lens. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the object plane, and a negative value indicates that the surface bends towards the image plane. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. Thickness represents the central axial distance between the current surface and the next surface. nd represents the refractive index, which represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current location is air with a refractive index of 1. vd represents the Abbe constant, which represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current location is air.

[0068] Table 3. Design values ​​of aspheric coefficients for different lenses in Example 1.

[0069]

[0070] The K value in Table 3 represents the magnitude of the conic coefficient of the aspherical surface; "-1.280223E-04" means -1.280223 * 10⁻⁴. -4 All other coefficients are represented in this way.

[0071] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0072]

[0073] Where Z is the sag of the aspherical surface, c is the fundamental curvature at the vertex, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and a i a is the coefficient of the higher-order term. i r 2i a2, a3, a4, a5, and a6 are the 4th, 6th, 8th, 10th, and 12th order coefficients of the aspherical polynomial, respectively.

[0074] The optical system in this embodiment achieves the following technical specifications:

[0075] Focal length: 5.352mm

[0076] Aperture: F2.52

[0077] Field of view: 143.6°

[0078] Overall optical length: 63.49mm

[0079] Image size: φ16.336mm.

[0080] Figure 2 This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Embodiment 1 of the present invention, specifically a schematic diagram of the spherical aberration curve with a pupil radius of 1.0292mm. The vertical direction represents the normalized 0 field-of-view pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex; the horizontal direction represents the spherical aberration of different wavelengths, in micrometers (μm). Figure 2 It can be seen that the spherical aberration under different wavelengths of light (0.436μm, 0.486μm, 0.588μm and 0.656μm) is within 0.07mm. As can be seen from the figure, the curves of different wavelengths are relatively concentrated, indicating that the spherical aberration of this fixed-focus lens is very small.

[0081] Figure 3 This is a distortion diagram of a fixed-focus lens provided in Embodiment 1 of the present invention, specifically a distortion diagram at a maximum field of view of 71.8°. In the diagram, the horizontal axis represents the magnitude of the distortion, in percentage (%); the vertical axis represents the normalized image height, which has no unit. Figure 3 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, with imaging distortion less than 50%.

[0082] In summary, the fixed-focus lens provided in this embodiment of the invention, by including eight lenses and rationally setting the surface shapes of the first, second, third, and eighth lenses, helps to reduce the difficulty of lens manufacturing, while improving lens illumination and sensitivity, balancing lens aberrations, and enhancing the imaging effect of the fixed-focus lens. This achieves a focal length of 5.352mm, an aperture of F2.52, a field of view of 143.6°, a total optical length of 63.49mm, and an image plane size of [missing information]. Optical systems that can be matched with 1″ target surface sensor chips.

[0083] Example 2

[0084] Figure 4 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of the present invention, as shown below. Figure 4As shown, the fixed-focus lens provided in Embodiment 2 of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180 arranged sequentially from the object plane to the image plane. The first lens 110 includes a first object-side surface near the object plane and a first image-side surface near the image plane, the first object-side surface being convex and the first image-side surface being concave. The second lens 120 includes a second object-side surface near the object plane and a second image-side surface near the image plane, the second object-side surface being convex and the second image-side surface being concave. The third lens 130 includes a third object-side surface near the object plane and a third image-side surface near the image plane, the third object-side surface being concave and the third image-side surface being convex. The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane, the eighth object-side surface being convex and the eighth image-side surface being convex.

[0085] The lens setup is the same as in Embodiment 1, and will not be repeated here.

[0086] As another feasible implementation method, the specific parameters of the fixed-focus lens are explained below.

[0087] Table 4. Optical design values ​​for a fixed-focus lens in Example 2.

[0088]

[0089] Table 5. Design values ​​for the surface type, radius of curvature, thickness, refractive index, Abbe number, and semi-diameter of each lens in a fixed-focus lens.

[0090] Face number Surface type radius of curvature thickness Materials (nd) Materials (vd) Half diameter S1 spherical 51.070 2.321 23.899 S2 spherical 23.218 3.503 1.823 33.195 15.805 S3 spherical 9.361 6.023 9.020 S4 spherical 41.828 1.051 1.752 33.191 8.897 S5 spherical 9.432 5.362 7.024 S6 aspherical -12.579 3.941 1.535 55.711 6.977 S7 aspherical -15.224 0.100 7.211 S8 spherical -69.692 7.740 1.753 28.916 6.937 S9 spherical -21.963 2.026 6.500 S10 spherical 9.323 8.001 1.613 61.694 5.109 S11 spherical -55.881 0.237 2.403 STO spherical PL 3.264 2.238 S13 spherical -6.533 0.699 1.747 26.000 3.060 S14 spherical 7.239 2.702 1.625 70.000 4.216 S15 spherical -16.289 0.099 4.606 S16 aspherical 13.000 4.331 1.535 55.711 6.500 S17 aspherical -8.589 0.171 6.822 S18 spherical PL 1.496 1.517 64.212 7.148 S19 spherical PL 5.846±0.5 7.271

[0091] In Table 5 above, the surface numbers are assigned according to the surface sequence of each lens. "S1" represents the object-side surface of the first lens, "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture stop of the lens. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the object plane, and a negative value indicates that the surface bends towards the image plane. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. Thickness represents the central axial distance between the current surface and the next surface. nd represents the refractive index, which represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current location is air with a refractive index of 1. vd represents the Abbe constant, which represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current location is air.

[0092] Table 6. Design values ​​of aspherical coefficients for different lenses in Example 2.

[0093]

[0094] The K value in Table 6 represents the magnitude of the conic coefficient of the aspherical surface; "1.939294E-05" means 1.939294 * 10⁻⁶. -5 All other coefficients are represented in this way.

[0095] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0096]

[0097] Where Z is the sag of the aspherical surface, c is the fundamental curvature at the vertex, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and a i a is the coefficient of the higher-order term. i r 2i a2, a3, a4, a5, and a6 are the 4th, 6th, 8th, 10th, and 12th order coefficients of the aspherical polynomial, respectively.

[0098] The optical system in this embodiment achieves the following technical specifications:

[0099] Focal length: 5.145mm

[0100] Aperture: F2.64

[0101] Field of view: 144.5°

[0102] Overall optical length: 56.59mm

[0103] Image size: φ16.105mm.

[0104] Figure 5 This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Embodiment 2 of the present invention, specifically a schematic diagram of the spherical aberration curve with a pupil radius of 0.9894 mm. The vertical direction represents the normalized 0 field-of-view pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex; the horizontal direction represents the spherical aberration of different wavelengths, in micrometers (μm). Figure 5 It can be seen that the spherical aberration under different wavelengths of light (0.436μm, 0.486μm, 0.588μm and 0.656μm) is within 0.02mm. As can be seen from the figure, the curves of different wavelengths are relatively concentrated, indicating that the spherical aberration of this fixed-focus lens is very small.

[0105] Figure 6 This is a distortion diagram of a fixed-focus lens provided in Embodiment 2 of the present invention, specifically a distortion diagram with a maximum field of view of 72.230°. In the diagram, the horizontal axis represents the magnitude of the distortion, in percentage (%); the vertical axis represents the normalized image height, which has no unit. Figure 6As can be seen, the distortion of the lens provided in this embodiment has been well corrected, with imaging distortion less than 50%.

[0106] In summary, the fixed-focus lens provided in this embodiment of the invention, by setting the fixed-focus lens to include eight lenses and by reasonably setting the surface shapes of the first lens, second lens, third lens and eighth lens, helps to reduce the lens manufacturing difficulty, while improving lens illumination and lens sensitivity, balancing lens aberrations, and improving the imaging effect of the fixed-focus lens. It achieves a focal length of 5.145mm, an aperture of F2.64, a field of view of 144.5°, a total optical length of 56.59mm and an image plane size of φ16.105mm, and can be matched with an optical system of a 1″ target surface sensor chip.

[0107] Example 3

[0108] Figure 7 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of the present invention, as shown below. Figure 7 As shown, the fixed-focus lens provided in Embodiment 3 of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180 arranged sequentially from the object plane to the image plane. The first lens 110 includes a first object-side surface near the object plane and a first image-side surface near the image plane. The first object-side surface is convex, and the first image-side surface is concave. The second lens 120 includes a second object-side surface near the object plane and a second image-side surface near the image plane. The second object-side surface is convex, and the second image-side surface is concave. The third lens 130 includes a third object-side surface near the object plane and a third image-side surface near the image plane. The third object-side surface is concave, and the third image-side surface is convex. The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane. The eighth object-side surface is convex, and the eighth image-side surface is convex.

[0109] The lens setup is the same as in Embodiment 1, and will not be repeated here.

[0110] As another feasible implementation method, the specific parameters of the fixed-focus lens are explained below.

[0111] Table 7. Optical design values ​​for a fixed-focus lens in Example 3.

[0112]

[0113] Table 8. Design values ​​for the surface type, radius of curvature, thickness, refractive index, Abbe number, and semi-diameter of each lens in a fixed-focus lens.

[0114] Face number Surface type radius of curvature thickness Materials (nd) Materials (vd) Half diameter S1 spherical 51.070 2.321 21.116 S2 spherical 23.348 2.000 1.803 49.001 13.839 S3 spherical 9.239 5.196 8.684 S4 spherical 38.223 0.764 1.736 54.680 8.599 S5 spherical 9.089 5.299 6.899 S6 aspherical -12.085 4.000 1.690 23.000 6.858 S7 aspherical -15.301 0.100 7.284 S8 spherical -65.209 7.964 1.731 55.000 7.000 S9 spherical -22.070 4.606 6.625 S10 spherical 9.267 7.952 1.617 60.000 4.300 S11 spherical -57.231 0.101 2.468 STO spherical PL 3.534 2.406 S13 spherical -6.548 0.701 1.756 26.003 3.114 S14 spherical 6.975 2.772 1.612 49.168 4.195 S15 spherical -15.959 0.310 4.587 S16 aspherical 13.319 5.042 1.533 53.106 6.400 S17 aspherical -8.549 0.033 6.896 S18 spherical PL 1.650 1.517 64.212 7.235 S19 spherical PL 6.159±0.5 7.356

[0115] In Table 8 above, the surface numbers are assigned according to the surface order of each lens. "S1" represents the object-side surface of the first lens, "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture stop of the lens. The radius of curvature represents the curvature of the lens surface; a positive value indicates that the surface bends towards the object plane, and a negative value indicates that the surface bends towards the image plane. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. Thickness represents the central axial distance between the current surface and the next surface. nd represents the refractive index, which represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current location is air with a refractive index of 1. vd represents the Abbe constant, which represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current location is air.

[0116] Table 9. Design values ​​of aspherical coefficients for different lenses in Example 3.

[0117]

[0118]

[01] The K value in Table 9 represents the magnitude of the conic coefficient of the aspherical surface. "4.006309E-05" means 4.006309 * 10 -5 All other coefficients are represented in this way.

[0119] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0120]

[0121] Where Z is the sag of the aspherical surface, c is the fundamental curvature at the vertex, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and a i a is the coefficient of the higher-order term. i r 2i a2, a3, a4, a5, and a6 are the 4th, 6th, 8th, 10th, and 12th order coefficients of the aspherical polynomial, respectively.

[0122] The optical system in this embodiment achieves the following technical specifications:

[0123] Focal length: 5.068mm

[0124] Aperture: F2.65

[0125] Field of view: 145.0°

[0126] Overall optical length: 58.18mm

[0127] Image size: φ16.113mm.

[0128] Figure 8This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Embodiment 3 of the present invention, specifically a schematic diagram of the spherical aberration curve with a pupil radius of 0.9746 mm. The vertical direction represents the normalized 0 field-of-view pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex; the horizontal direction represents the spherical aberration of different wavelengths, in micrometers (μm). Figure 8 It can be seen that the spherical aberration under different wavelengths of light (0.436μm, 0.486μm, 0.588μm and 0.656μm) is within 0.02mm. As can be seen from the figure, the curves of different wavelengths are relatively concentrated, indicating that the spherical aberration of this fixed-focus lens is very small.

[0129] Figure 9 This is a distortion diagram of a fixed-focus lens provided in Embodiment 3 of the present invention, specifically a distortion diagram at a maximum field of view of 72.500°. In the diagram, the horizontal axis represents the magnitude of the distortion, in percentage (%); the vertical axis represents the normalized image height, which has no unit. Figure 9 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, with imaging distortion less than 50%.

[0130] In summary, the fixed-focus lens provided in this embodiment of the invention, by setting the fixed-focus lens to include eight lenses and by reasonably setting the surface shapes of the first lens, second lens, third lens and eighth lens, helps to reduce the lens manufacturing difficulty, while improving lens illumination and lens sensitivity, balancing lens aberrations, and improving the imaging effect of the fixed-focus lens. It achieves a focal length of 5.068mm, an aperture of F2.65, a field of view of 145.0°, a total optical length of 58.18.59mm and an image plane size of φ16.113mm, and can be matched with an optical system of a 1″ target surface sensor chip.

[0131] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A fixed-focus lens, characterized in that, It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis from the object plane to the image plane; The first lens has negative optical power; the second lens has negative optical power; the third lens has negative optical power; the fourth lens has positive optical power; the fifth lens has positive optical power; the sixth lens and the seventh lens are cemented together to form a cemented lens, and the cemented lens has negative optical power. The eighth lens has positive optical power; The optical power of the fixed-focus lens is φ, the optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the optical power of the fifth lens is φ5, the optical power of the cemented lens is φ67, and the optical power of the eighth lens is φ8. Among them: -0.349<φ1 / φ<-0.132; -0.413<φ2 / φ<-0.126; -0.130<φ3 / φ<0.000; 0.000< φ4 / φ<0.229; 0.265<φ5 / φ<0.476; -0.545<φ67 / φ<-0.314; 0.373<φ8 / φ<0.595; The first lens includes a first object-side surface near the object plane and a first image-side surface near the image plane. The first object-side surface is convex, and the first image-side surface is concave. The second lens includes a second object-side surface near the object plane and a second image-side surface near the image plane, wherein the second object-side surface is convex and the second image-side surface is concave. The third lens includes a third object-side surface near the object plane and a third image-side surface near the image plane, wherein the third object-side surface is concave and the third image-side surface is convex. The fourth lens includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane; the fourth object-side surface is concave and the fourth image-side surface is convex. The fifth lens includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane; the fifth object-side surface is convex, and the fifth image-side surface is convex. The sixth lens includes a sixth object-side surface near the object plane and a sixth image-side surface near the image plane; the sixth object-side surface is concave and the sixth image-side surface is concave. The seventh lens includes a seventh object-side surface near the object plane and a seventh image-side surface near the image plane; the seventh object-side surface is convex and the seventh image-side surface is convex. The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane. The eighth object-side surface is convex, and the eighth image-side surface is convex.

2. The fixed-focus lens according to claim 1, characterized in that, The first lens, the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all glass spherical lenses, while the third lens and the eighth lens are both plastic aspherical lenses.

3. The fixed-focus lens according to claim 1, characterized in that, The sixth lens and the seventh lens are cemented together to form a cemented lens.

4. The fixed-focus lens according to claim 1, characterized in that, The refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n2, the refractive index of the fourth lens is n4, the refractive index of the fifth lens is n5, the refractive index of the sixth lens is n6, the refractive index of the seventh lens is n7, and the refractive index of the eighth lens is n8. Among them, 1.72≤n1≤1.87; 1.57≤n2≤1.80; 1.49≤n3≤1.74; 1.54≤n4≤1.80; 1.49≤n5≤1.67; 1.70≤n6≤1.84; 1.56≤n7≤1.86; 1.48≤n8≤1.

69.

5. The fixed-focus lens according to claim 1, characterized in that, The image plane diameter of the fixed-focus lens is IC, and the total length of the fixed-focus lens is TTL; Among them, IC / TTL≥0.

24.

6. The fixed-focus lens according to claim 1, characterized in that, The field of view (FOV) of the fixed-focus lens satisfies FOV > 140°.

7. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens also includes an aperture stop and a filter; The aperture stop is disposed in the optical path between the fifth lens and the sixth lens; The filter is disposed in the optical path between the eighth lens and the image plane.

Images